The Pygmy Alligator Lizard of Nuevo León, Mexico

Overhead, the laughing call of a
canyon wren momentarily distracted
my focus from the rattlesnake I was
watching just 2 feet in front of me.
What had started off as a rock-collecting trip through the bottom of a steepwalled limestone canyon south of Monterrey,
Nuevo León (Mexico), had turned into a
snake-collecting trip — and now I was
waiting patiently in the afternoon sun for Javier to return
from the truck.
Javier Banda-Leal is a student at the Universidad Autónoma de Nuevo León (UANL) in Monterrey. When we stumbled onto the tiny
rock rattlesnake we were carrying only
one bag for rocks, so Javier made a quick
beeline back to the truck for our snake collecting
equipment, leaving me to keep an eye on our newfound friend. For several years I had been collaborating with researchers at UANL on the captive breeding
of montane rattlesnakes, and this new specimen would
make a great addition to the school’s captive collection.
The little rattlesnake was still calmly
coiled at the base of the rock where
we’d found it when Javier reappeared.
I was silently feeling thankful for our
good luck, and then I noticed that Javier was
walking very slowly and staring at his hand.
When he got closer, I saw that he had caught
a lizard. “What the heck is this?” he asked,
holding it out for me to see.
As I looked at the tiny lizard squirming in his
hands, a sudden wave of excited disbelief
came over me. Amazingly, our luck in finding
the rock rattlesnake had already been surpassed — we had just found the third known
specimen of the rare, endemic pygmy alligator
lizard of Nuevo León!
Natural history
The pygmy alligator lizard, Gerrhonotus parvus
Knight and Scudday, 1985, is the smallest known
species of anguid lizard, reaching a total length of
only 55–72.5 millimeters (one huge adult measured
76.5 millimeters!) snout-vent length. The tail is typically about twice the SVL. This species is oviparous.
The Pygmy Alligator Lizard of Nuevo León, Mexico
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Gerrhonotus parvus. Photo: D. Lazcano
The paratype was a 71.7-millimeter
(SVL) female that was maintained
in captivity for 5 years and reportedly laid several clutches of eggs
before her death. The species is
endemic to Nuevo León, Mexico,
and has been collected from February to October in arid transition
woodland characterized by oak,
agave, sotol, and extensive outcrops of exposed limestone, at elevations of 5,250–5,415 feet (ca.
1,600–1,650 meters).
During the course of our fieldwork on montane rattlesnakes, we
have now found a total of five
specimens of pygmy alligator lizard.
Gerrhonotus infernales is sympatric with Gerrhonotus parvus. Photo: D. Lazcano
One was found under a dead yucca
in a garbage dump south of
Galeana, the type locality of the
species. Three of the other four
(including the one mentioned at the
beginning of this article) were found
west of San Isidro in a canyon (ca.
5,250 feet above sea level) running
east to west, with scattered piles of
leaf litter, large rocks, and an intermittent stream that leaves pools of
water (most of which dry up during
the dry season).
Near Galeana, the pygmy alligator lizard’s distribution
area is also home to the pine woods
shortnose skink, Eumeces brevirostris
pineus ; the northern mesquite
lizard, Sceloporus grammicus
disparilis; the northern bluebelly
lizard, S. parvus parvus; the spiny
lizard, S. spinosus spinosus; the
Nuevo Leon crevice swift, S.
torquatus binocularis; the Texas
night snake, Hysiglena torquata
jani; the San Luis Potosi kingsnake,
Lampropeltis mexicana; Jan’s bullsnake, Pituophis deppei jani; the
Texas patchnose snake, Salvadora
Typical Gerrhonotus parvus habitat. Photo: R. Bryson
Gerrhonotus parvus. Photo: D. Lazcano
grahamiae lineata; the western
blackneck garter snake, Thamnophis
cyrtopsis cyrtopsis; the western diamondback rattlesnake, Crotalus
atrox; the blacktail rattlesnake, C.
molossus molossus; the Mojave rattlesnake, C. scutulatus scutulatus;
the coastal plain toad, Bufo nebulifer;
and the Rio Grande chirping frog,
Eleutherodactylus cystignathoides
campi. In the canyon near San
Isidro, the pygmy alligator lizard is
sympatric with the Texas alligator
lizard, Gerrhonotus infernalis —
and this distribution area is also
home to Couch’s spiny lizard,
Sceloporus couchi ;
the northern
mesquite lizard; the northern bluebelly lizard; the Nuevo Leon
crevice swift; Ruthven’s whipsnake, Masticophis taeniatus
ruthveni; the Nuevo Leon graceful
brown snake, Rhadinaea montana;
the Texas patchnose snake; Sartor’s snail sucker, Sibon sartori
sartori; the arid land ribbon snake,
Thamnophis proximus diabolicus;
the mottled rock rattlesnake,
Crotalus lepidus lepidus ; the
blacktail rattlesnake; the coastal
plain toad; the Rio Grande chirping frog; and the long-footed
chirping frog, Eleutherodactylus
longipes.
Taxonomic confusion
KNIGHT and SCUDDAY (1985)
described the pygmy alligator lizard and named it
Gerrhonotus parvus
— assigning the
taxon to this
genus
Gerrhonotus parvus. Photo: D. Lazcano
because of its perceived close relationship with Lugo’s alligator
lizard, G. lugoi, from the Cuatro
Ciénegas Basin in Coahuila. Only
a year later, however, SMITH
(1986) assigned the species to the
genus Elgaria based on head scalation. Nonetheless, recent molecular work (CONROY et al., in
press) has shown the pygmy alligator lizard to indeed belong to the
genus Gerrhonotus as originally
described.
The pygmy alligator lizard is distinguished from all other species
of the family Anguidae by the following combination of characteristics: smooth dorsal scales, the rostral in contact with the nasals, a
second primary temporal that is in
contact with the fifth medial
supraocular, suboculars separated
from the lower primary temporal
by an upper labial, and wide pale
crossbands on the tail (KNIGHT
and SCUDDAY, 1985).
Captive Husbandry
The pygmy alligator lizard has
proven to be a hardy captive. At
the herpetology lab at UANL,
three specimens have been kept
for more than 2 years with no
problems. This species seems to
be less aggressive than other
anguids — such as the sympatric,
larger Gerrhonotus infernalis —
but they do occasionally twist
around and bite.
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Other species that are also found within the range of Gerrhonotus parvus
Sibon sartori sartori. Photo: D. Lazcano
Coluber constrictor oaxaca. Photo: D. Lazcano
Coluber constrictor oaxaca. Photo: D. Lazcano
Crotalus lepidus. Photo: R. Bryson
The UANL specimens have been housed individually in plastic shoeboxes measuring 35 x 23 x 15 centimeters, with numerous holes drilled in the top and
sides for ventilation. Each enclosure has a small
water bowl, a small plastic hide box, and a newspaper
substrate that is changed daily. The lizards are usually fed vitamin/calcium-dusted crickets every 3–4 days,
and mealworms once a month. The room temperature is usually maintained at 77°F (25°C) during the
day, and 70°F (21°C) at night. During the winter,
these temperatures drop by about 5 degrees Fahrenheit (about 3 degrees Celsius). No other enclosure
heating is used. No artificial lighting is used. The
enclosures are exposed to natural indirect light that
comes in through the windows, with the natural photoperiod of Monterrey.
Recently, the lizards have been transferred to allglass aquariums measuring 60 x 50 x 30 centimeters,
with screen tops. The substrate is cypress mulch, and
each enclosure has a small water dish and a hide box.
The mulch substrate is spot cleaned and the water
dishes are cleaned and refilled once a week. The
enclosures are misted lightly two or three times a
week.
We have recently been able to sex the lizards, and
found that all three are males (by hemipenal “popping”).
Eleutherodactylus c. campi. Photo: D. Lazcano
If we can obtain a female, we would like to breed the
species. We would hibernate the lizards for 3–4
months at 55–60°F (13–16°C), and then put males and
females together within 2–3 weeks of removal from
hibernation. We would provide overhead basking
lights and a nest box to allow a gravid female to thermoregulate and lay eggs.
It is hoped that we will succeed in reproducing this
species in captivity. The experience of finding the
unique and rare pygmy alligator lizard of Nuevo León
in the wild is thrilling, and could only be approximated by the experience of hatching babies in the lab!
Note: All research has been conducted with permits
issued by the Mexican government.
■
Bibliography
CONROY, C. J., R. W. BRYSON, D. LAZCANO, and A.
KNIGHT. In press. The phylogenetic position of the pygmy alligator lizard (Elgaria parva) based on molecular data. Journal of
Herpetology.
KNIGHT, R. A., and J. F. SCUDDAY. 1985. A new Gerrhonotus
(Lacertilia: Anguidae) from the Sierra Madre Oriental, Nuevo
León, Mexico. Southwestern Naturalist 30: 89–94.
SMITH, H. M. 1986. The generic allocation of two species of
Mexican anguid lizards. Bulletin of the Maryland Herpetological
Society 22: 21–22.
WADDICK, J. W., and H. M. SMITH. 1974. The significance of
scale characters in evaluation of the lizard genera Gerrhonotus,
Elgaria, and Barisia. Great Basin Naturalist 34: 257–266.
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